Work following apparatus



May 26, 1942. T. F. BRACKETT 2,284,557

woRx FOLLOWING APPARATUS Filed Oct. 2, 1941 3 Sheets-Sheet l Snventor we zzwww,

22% M I attornegs May 26, 1942. T. F. BRACKETT 2,284,557

WORK FOLLOWING APPARATUS 1 Inventor Gttornegs May 26, 1942.

1'. F. BRACKETT' 2,284,557 WORK FOLLOWIFNG AP PARATUS Filed Oct. 2, 1941 3 Sheets-Sheet 3 PH +--H f QI U Z'Srwentor Qiacy J7 5736/8622 Patented May 26, 1942 UNITED STATES PATENT OFFICE WORK FOLLOWING APPARATUS Tracy F. Brackett, Detroit, Mich, assignor to General Motors Corporation, Detroit, Mich, a

corporation of Delaware Claims.

This invention relates to factory equipment and more particularly to apparatus for surface finishing roofs of automobile bodies traveling on a conveyor system through the paint shop. As a part of the surface finishing operation the assembled body walls are sanded and sprayed with paint with the work on the roof surface being done from overhead. Currently styled bodies have longitudinally curved roofs and provision is here made to maintain a working relation on the contoured roof surface as it travels through the working zone of the surface treating device, preferably by shifting the body in compensation for or in accordance with variations in roof height.

It is among the objects of the invention to provide a hinged track section as part of the conveyor system and which can be swung to raise or lower the body carrying conveyor truck or a portion thereof, together with track operating mechanism and a control system therefor, which acts automatically in accordance with the height of the body roof surface presented in the working zone by conveyor travel and serves to raise or lower the body carrying truck so that the body roof surface follows a proper path for action thereon by the surface finishing device.

In a preferred embodiment of the invention a hinged track section is adjustable vertically by an electric motor operable in either direction with motor control switches responsive primarily to the actuation of a photoelectric cell positioned to receive a light beam projected across the path of body travel at approximately the roof level in the working zone. In other words. should the roof surface recede from the working zone the photocell immediately catches the light beam and the electric motor responds to the energization of a control circuit and raises the body to the proper working level in which the light beam is again interrupted. Reversal of the motor lowers the track appropriately as called for by the shape of the surface operated upon, but in the case of the conventional automobile body having a roof of substantially continuous rearward taper, the elevation of the track will occur in substantially constant relation to the travel of the body until the desired limit is reached, at which time the track will move all the way down and await operation upon the next body in line. The motor control circuit preferably includes safety features, such as upper and lower limit switches to prevent overruning in either direction as well as emergency hand operated switches.

In the accompanying drawings Figure 1 is a side elevation with parts in section showing an automobile body on a portion of the conveyor system in the working zone of an abrader; Figure 2 is a longitudinal sectional view of the track operating linkage and is taken substantially on line 2-2 of Figure 4; Figure 3 is a transverse section taken on line 3-3 of Figure 2; Figure 4 is a top plan View showing the hinged track section and its operating mechanism and Figure 5 is a wiring diagram illustrating a simplified version of the control circuit.

In the drawings the reference numeral I indi cates a surface finishing tool, such as a sander or polisher, which is fixedly located above the usual conveyor line for action on the roof. of an automobile body 2 as the body travels beneath the abrader I. As shown in Figure 1 the roof of the body is substantially horizontal near the front portion and recedes or tapers in height toward the rear of the body. Immediately. adjacent the working zone of the abrader l and approximately level with the roof surface operated upon is located as at 3 a photoswitch. The photocell is located on one side of the assembly line and has focused on it a source of light positioned on the opposite side of the assembly line so that the light beam is interrupted by the roof of the body when the roof surface is at the proper level to be operated upon. Should the receding roof surface move out of the light beam, as will be the case as the body travels forward, a motor control circuit is energized through response of the photoswitch, for raising the body as indicated by the broken lines in Figure 1.

For the purpose of shifting the body vertically, the guide track for the wheels of the body carrying truck or dolly 4 contains hinged sections 5 and 6 which normally form horizontal portions of the conveyor track. These hinged sections, one set on each of the transversely spaced track rails, have their adjacent ends pivotally connected as at l with the remote end of the section 5 hingedly mounted at 8 on a horizontal transverse axis and the remote end of the section 6 slidable on a floor bearing plate. The hinge connection may consist of a pair of outwardly extending trunnions mounted in suitable bearings as best seen in Figure 4. When the rearmost wheels of the truck engage the hinged section 5, elevation of the track sections will raise the rear end of the body as called for by the relative height of the abrader l and the normal height of the roof surface to be operated upon.

Near the swinging end of each hinged track section 5 are welded or otherwise secured a pair of outwardly extending wings or plates 9-4 against the underside of which ride rollers It] in the lift levers ll. Each pair of operating levers II is fixed to a transverse rockshaft 12 mounted in suitable bearings and projecting out beyond the side of the conveyor track where it is provided with'the crank 12'. The cranks l2 on the two sides of the track are joined by connecting rods l3--!3 to swinging levers I L-l4 secured to vertical posts I5 which are pivotally mounted in supporting brackets It. At their lower ends the posts :5 carry levers I! which are interconnected by a tie bar l8 extending under the trackway and coupling the two sets of operating linkages for conjoint operation,

Operation of the linkage is effected through a power unit comprising an electric motor l9 driving through a gear reduction box 20, a crank arm 2! connected by the pull rod 22 with the adjoining end of a connecting rod l3. The shaft to which the crank 2! is secured projects beyond the opposite side of the gear box where it carries a crank 23 through which the operation of the motor, raising or lowering the track, is transmitted for operating upper and lower limit switches in the motor control circuit.

The upper and lower limit switches are indicated in the wiring diagram, Figure 5, at 24 and 25, respectively. Each has an actuating arm adapted to be engaged selectively by a camming. shoe 26 when the hinged track section reaches its upper or lower limit as the case may be. rod 21 secured to one end of a rock lever 28 Whose opposite end is joined to the crank arm 23. Movementof the crank arm 23 is also transoperating handle is arranged to be tripped by a suitable abutment, such as indicated at 34, carried b the conveyor truck 4. Upon actuation of the air cylinder 32 in this manner the lever 3| is swung to a position in which the light switch 35 closes a circuit to the light source 36 from the transformer 31, providing the hand switch 38 is engaged with the switch contact 39. This conditions the automatic control system whereby if the roof surface moves-out of the beam from the light 36 to the photocell 3, operating current from the transformer 31 will be supplied to a relay (it which closes the switch 4| and supplies actuating current through the safety switch 24 to the solenoid 42 whereby the motor circuit is closed for operating the motor IS in the track elevating direction.

Operation of the, motor when the solenoid 42 closes the motor circuit switch will raise the hinged track sections 5 and B and also swing the crank 23 in a counterclockwise direction as viewed in Figure 5, moving the cam 25 to allow the safety switch 25 to be closed. Operation of the motor will continue to raise the roof until the light beam to the photocell 3 is again interrupted when switch Al is opened and its companion switch 43 closed in a circuit containing the timer 44 as well as the switch 25 and a solenoid t5, the latter of which controls a switch in the motor circuit for reversing the direction of operation and lowering the track. However,- the The cam shoe 26 is mounted on a slide' reversal does not take place immediately because the timer 44 introduces a sufficient lag to prevent erratic up and down operation of the lift. As the body continues to travel through the working zone and usually until the rear window opening is reached by the buffer, the light beam repeatedly reaches the photocell for continued upward movement until such predetermined limit is reached in which sufficient force is stored within the spring 39 as the crank arm 23 has swung over, to snap the lever 3| back to original position for opening the light circuit. In addition to opening the switch 35 the interconnected switch 46 will be closed, immediately completing a circuit through the safety switch 25 to the solenoid 45, whereby the motor circuit switch is closed for lowering the track. As soon as the downward limit is reached the safety switch 25 opens and the operation of the motor stops and the system is inoperative until the air cylinder 33 is again actuated in response to the travel of the succeeding body truck.

Should the automatic system become defective or in the event it is necessary to operate the system for testing purposes or otherwise, the switch 38 may be engaged with the contact 4] leading to a two-Way switch 48 which may be thrown by hand to supply operating current to either the up or the down motor control circuits.

I claim:

1. For performing work on the roof of a traveling body whose roof surf-ace varies in height in the direction of travel, a, surface working device having a fixed location above the path of body travel, a conveyor system including a wheeled dolly adapted to carry a body through the working zone of said device, means to shift the dolly vertically in relation to the device and. control mechanism for said means responsive to the height of the roof presented at said working zone for maintaining the roof surface in working relation with the device. 4

2. In apparatus of the character described, a surface treating device, a traveling dolly adapted to carry a body whose roof surface to be treated is longitudinally curved, a track engaged by the dolly, means to raise the track in compensation for roof curvature to maintain the, roof surface in the working zone of the device and mechanism responsive to the height of the roof surface at the working zone for actuating said means.

3. Factory apparatus of the type described, including a traveling truck adapted to carry a body whose roof varies in height in the direction of truck travel, a work performing device operable on said roof, a track eng-ageable by the truck and hinged on an axis transverse to the direction of truck travel for vertical swinging adjustment, actuating mechanism for adjusting the track and means responsive to the height of the roof surface presented in the working zone of said device to regulate said actuating mechanism.

4. For performing work on the longitudinally curved roof surface of a traveling body, surface working mechanism, a traveling truck adapted to carry a body and present its roof in the working zone of said mechanism, means to raise and lower said truck in relation to the mechanism, a photocell control for said means and a source of light directed to the photocell control and through the path of the roof surface presented to said mechanism.

5. Industrial equipment comprising a traveling truck adapted to carry a body having a wall surface curved in the direction of truck travel, Work performing mechanism operable on said surface and located in fixed relation to the path of truck travel, movable means to shift the truck in relation to said mechanism as the wall surface travels through the working zone thereof in compensation for the surface curvature and actuating mechanism for said means including a reversihle motor operably connected with said means, a photoswitch controlling power feed to said motor and a light beam source for said photoswitch directed across the path through which the wall surface travels for operation thereon by said Work performing mechanism.

TRACY F, BRACKETT. 

